Portable muscle stimulator with pulse width control

ABSTRACT

A portable muscle stimulator with removable data storage card is disclosed in which the removable data storage card is secured within the power muscle stimulator on specially designed rail guides which prevent the removable data storage card from being inserted to the power muscle stimulator incorrectly and which ensure that the power muscle stimulator is secured in a removable fashion within the power muscle stimulator. The portable muscle stimulator include a multitude of safety features which are designed to prevent injury to the user while at the same time to ensure that the portable power muscle stimulator is easy to use.

This is a continuation of application Ser. No. 08/536,924, filed Sep.29, 1995 now U.S. Pat. No. 5,755,745.

BACKGROUND OF THE INVENTION

The present invention relates generally to portable muscle stimulatorsfor unsupervised personal use. More particularly, the present inventionrelates to a method of and system for providing a portable musclestimulator with a mechanism which provides usage monitoring capability.

With the increasing application of high technology to medicalapplications, there has been a trend in recent years to providing asmuch care as possible as well as sophisticated medical treatment outsideof hospitals. That trend has resulted in an increase in the amount ofsurgery as well as other types of medical treatment, such asrehabilitation services, being performed outside of hospitals in, forexample, ambulatory surgery centers or rehabilitation centers,respectively.

In order to provide an even more cost effective outcome, technology isbeing applied to obtain the desired medical outcome with medicalequipment that can be utilized in the patient's home. In addition to thecost advantages obtained over providing similar treatment in anoutpatient setting, the use of such devices by patients in their homesis also more convenient for the patients, since they do not need totravel to an outpatient center for treatment, and they can initiatetheir own unsupervised treatment at their convenience.

However, several issues which were not concerns when the treatmentservices were provided to patients in an outpatient or hospital setting,quickly become concerns when patients supervise their own treatment intheir own living areas. First, the device which the patients operate toeffectuate their prescribed treatment must be easy to use and must bemade as safe to use as possible. Second, it would be desirable to beable to monitor and therefore document the use of the device by thepatient, in order to assure that the protocol desired for the patient isbeing utilized. By obtaining such usage data, the physician/health careproviders who have developed and/or prescribed the protocol for use bythe patient can be satisfied that the patient is indeed performing thedesired protocol and the patient's progress can be measured. Inaddition, the underwriter of the cost of the treatment can be assuredthat the patient is actually following the protocol. Such monitoring isimportant in connection with all of the Class II devices, as they aredefined in the Food and Drug Administration's Manual, "ClassificationNames for Medical Devices and In Vitro Diagnostic Products," such as apowered muscle stimulator as defined in 21 C.F.R. 890.5850. Such ClassII devices are regulated and require a prescription by a doctor but donot require a high degree of supervision. Thus, such devices are usedpersonally by the patient for whom they are prescribed without anysupervision at the time of use.

SUMMARY AND OBJECTS OF THE INVENTION

In view of the foregoing, it should be apparent that there still existsa need in the art for a method of and apparatus for a portable musclestimulator which includes a usage monitoring capability for capturingand storing information with respect to the use of the device by apatient. It is, therefore, a primary object of this invention to providea method of and apparatus for a portable muscle stimulator device havinga usage monitoring and storage capability which is characterized bysimple electronic circuitry and which has particular application forunsupervised personal use by a patient.

More particularly, it is an object of this invention to provide apowered muscle stimulator device as described above having reliableelectronic circuitry and software which can be easily and safely used byan unsupervised patient.

Still more particularly, it is an object of this invention to provide apowered muscle stimulator device which uses a ramp-on/off style ofstimulation which is more comfortable to the patient than the previouslyused abruptly changing stimulation approach.

Another object of the present invention is to provide several additionalsafety features which both enhance the patient usability and safety ofthe powered muscle stimulator invention disclosed herein. These featuresare designed to prevent user error and accidental use and to assurecorrect operation of the powered muscle stimulator itself.

Briefly described, these and other objects of the invention areaccomplished in accordance with its apparatus aspects by providing aremovable data storage card which is secured within the powered musclestimulator on specially designed guide rails which prevent the removabledata storage card from being inserted into the powered muscle stimulatorincorrectly. The design of the guide rails also functions to removablysecure the data storage card in the correct location within the poweredmuscle stimulator itself. In addition, the pins on the pad cables usedwith the muscle stimulator are designed with a large diameter so thatthey cannot be plugged into a typical household 110 volt electricaloutlet. In addition, the battery charger cable pin is designed such thatit can only plug into the battery charger jack and not into a channeljack, which could damage the powered muscle stimulator.

In its method aspects, the powered muscle stimulator of the presentinvention is designed to detect if a connection between the pads, cablesand the stimulator is faulty and to take appropriate action. The poweredmuscle stimulator of the present invention is also designed such that achannel output level can be changed only by a single digit at a time,which assures that a rapid increase or decrease in muscle contractionwill not be experienced by the user during treatment if the rockerswitch was continually depressed.

Other safety features of the powered muscle stimulator includemonitoring the battery charger so that none of the channels of thepowered muscle stimulator can provide an output to a cable and pad whilethe battery is being recharged, constantly monitoring the frequency andwidth of the waveform output by the powered muscle stimulator and takingappropriate action if the waveform changes from the desired pattern,monitoring the liquid crystal display of the powered muscle stimulatorand taking appropriate action if the display is not operating properlyand constantly monitoring the battery voltage of the powered musclestimulator and taking appropriate action if the amount of voltagesupplied to the microprocessor is incorrect.

An additional safety and treatment feature of the powered musclestimulator of the present invention is that the stimulus intensityregulated by the patient is the pulse width of the voltage signal whichforms the output from each of the channels of the powered musclestimulator. A ramp on/off type of stimulation is utilized such that thepatient experiences a slowly increasing stimuli which is morecomfortable than an abruptly changing stimuli used in prior art devices.

With these and other objects, advantages and features of the inventionthat may become hereinafter apparent, the nature of the invention may bemore clearly understood by reference to the following detaileddescription of the invention, the appended claims, and to the severaldrawings attached herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a drawing of a top view of the powered muscle stimulator ofthe present invention;

FIG. 1B is a drawing of a side view of the powered muscle stimulatorshown in FIG. 1A;

FIG. 2 is a drawing of a front perspective view of the powered musclestimulator of the present invention showing the data storage card foruse therewith;

FIG. 3 is a drawing of a side view of the data storage card shown inFIG. 2;

FIG. 4 is a drawing of an end view of the data storage card shown inFIGS. 2 and 3;

FIG. 5 is a drawing of a cross section of the data storage card of thepresent invention taken along the line 5--5 of FIG. 3;

FIG. 6 is a drawing of a cross section of the data storage card of thepresent invention taken along the line 6--6 of FIG. 3;

FIG. 7 is a drawing of a front view of the powered muscle stimulatorshown in FIG. 1 showing some of the components located inside thestimulator;

FIG. 8 is a drawing of a section taken along the line 8--8 of FIG. 7;

FIG. 9 is a drawing of a side view of a guide rail used in FIG. 7;

FIG. 10 is a drawing of a top view of the guide rail used for securingthe data storage card in the powered muscle stimulator of the presentinvention;

FIG. 11 is a drawing of an enlarged detail of the back portion of theguide rail shown in FIG. 8 designated by circle 11--11;

FIG. 12 is a schematic block diagram of the circuitry of the poweredmuscle stimulator of the present invention;

FIG. 13 is a schematic block diagram showing the operation of thesoftware used to operate the powered muscle stimulator of the presentinvention; and

FIG. 14 is a diagram of the ramp structure for each of the outputimpulses produced by the powered muscle stimulator of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now in detail to the drawings wherein like parts aredesignated by like reference numerals throughout, there is illustratedin FIG. 1A a top view of the powered muscle stimulator 100 of thepresent invention. The powered muscle stimulator 100 includes a powerswitch 102 and four switches 104-110 for controlling the respectiveoutputs of each of the four isolated channels contained in the poweredmuscle stimulator 100. An LCD display 114 is provided as a userinterface. Four output jacks 116-122 are provided at the front of thecase of the powered muscle stimulator 100, a separate jack for each ofthe output channels. Each of the above-described components, togetherwith the circuitry and a nickel cadmium battery system 1208, as well asother components to be described later herein, are housed within theplastic case or shell 112 of the muscle stimulator 100.

As shown in FIG. 1B, the case or shell 112 of the muscle stimulator 100may be formed from an upper piece 112a and a lower piece 112b, in orderto more easily manufacture the muscle stimulator 100. A jack 124 forconnecting the muscle stimulator 100 to a battery charger 1210, may belocated on, for example, the right side of the muscle stimulator 100.

The muscle stimulator 100 may be used in a self-administered manner bypatients for providing treatments prescribed by physicians and/or otherhealth care providers. The muscle stimulator of the present inventionmay be used for the relaxation of muscle spasms, for the prevention orretardation of muscle disuse atrophy, for increasing local bloodcirculation in the legs or other limbs of the patient, for reeducatingthe leg muscles or other muscles of the patient, for providing immediatepost-surgical stimulation of calf muscles of the patient in order toprevent venous thrombosis, or for maintaining or increasing the range ofmotions of the patient's legs or other limbs.

In order to connect the output jacks 116-122 of the muscle stimulator100 to the patient, a like plurality of cables (only one cable 126 isshown for purposes of simplicity) is used to make a connection betweenone of the output jacks and a standard electrode pad (not shown) whichcontacts the skin of the patient. For safety purposes, the pin 128 ofthe cable 126 which is inserted into the respective jacks 116-122 inorder to connect the electrode pad to the respective outputjack may beformed of such a shape and size that it is not possible to plug the pin128 into a standard household plug which provides 110 volts ofelectricity. The pin 128 may preferably be a 2.5 mm diameter femaleplug.

The powered muscle stimulator 100 of the present invention is adigitally controlled device which provide additional safety features forthe user, other than those previously described. The muscle stimulatorprovides four isolated channels capable of independently treating fourseparate muscle groups. Each of the four channels has independent outputpower stages and transformers in order to provide channel separation.The muscle stimulator 100 is battery powered in order to provideportability. The battery power is provided by an internal six voltnickel cadmium battery system 1208, which eliminates the need forpatients to monitor and replace batteries. The user interface LCD 114provides visual feedback to the user. In addition, the circuitry of themuscle stimulator 100 includes a buzzer 1214 having an output whichprovides audible reinforcement of keystroke actions. Also, each of theisolated channels has a separate intensity control for independentlyincreasing and decreasing the intensity of that channel.

The power switch 102, in addition to powering on the muscle stimulator100, also serves as an off switch for shutting down the device. Theremaining operational functions, such as the contract or on time andrelax or off time, treatment time and normal/alternating mode selectionhave built-in default settings in firmware of 2 seconds, 2 seconds 40minutes and normal, respectively. However, as will be described laterherein, those default settings are easily modified at the time of use,in accordance with the prescription or the user's physician'sinstructions.

As shown in FIG. 2, the muscle stimulator 100 may be provided with adata storage card 200, the details of which are more fully shown anddescribed in connection with FIGS. 5-11. The data storage card consistsprimarily of a printed circuit board with a model 24 LC 16B serialEEPROM integrated circuit which is generally connected to variouscontacts of a header connector 400 having a plurality of contacts 402.In the preferred embodiment, such contacts 402 are female electricalcontacts. The header 400 is mounted at one end of the data storage card200 such that, when the data storage card slides into the musclestimulator 100 and is positioned by means of the guides 202 and 204 andelongated slots 600 and 602, the contacts 402 of the header 400 fit overthe contacts 208 of the header connector 206 mounted inside the musclestimulator 100.

The data storage card 200 is preferably provided with a "handle" 210which is formed in the bottom half 212 of the data storage card 200. Thetop 204 of the data storage card 200, like the bottom 212, is formedfrom a plastic material. The top 204 and bottom 212 portions may besecured together by means of screws 500 and 502 (shown in FIGS. 5 and6), glue or other suitable adhesive material. When the data storage card200 is mounted and properly seated within the muscle stimulator 100, theoutside edge of the data storage card 200 serves as a continuation ofthe normal edge of the muscle stimulator 100.

The bottom portion 212 of the data card 200 has integrally moldedelongated slots 600 and 602 which slidably engage with the respectiveguide rails 204 and 202. Adjacent to the front end of the data storagecard 200, a respective stop 300, 302, is provided on each side to ensurea positive stop when the data storage card 200 is properly seated in themuscle stimulator 100.

It should be understood that the elongated slots 600 and 602 are formedas a part of the data card 200 in such a manner that alignment of thedata card 200 in the muscle stimulator 100 is ensured because the slots600 and 602 only allow the data storage card 200 to be inserted into themuscle stimulator 100 with the correct orientation. That is, theelongated or tracking slots 600 and 602 are formed in such a manner thatthe data storage card 200 cannot be inserted upside down into the musclestimulator 100.

As shown in the figures, the printed circuit board (not shown) is fullyenclosed within the plastic data storage card 200 and covered such that,after the top and bottom portions 212 and 214 of the data storage cardshell are secured to each other, all of the internal componentscontained on the printed circuit board are protected from the outsideelements. In addition, the external header connector 400 is designedsuch that it contains cone shaped guides where are these shown?! moldedinto its plastic shape such that it assists in the alignment of theinternal header connector 206 mounted in the muscle stimulator 100.

The structure of the storage card 200 is such that it is designed to beused with and removed by the patient from the muscle stimulator 100, orany other similar type of Class II device which a patient uses in anunsupervised manner, mailed to a service bureau for downloading thestored usage information, and replaced with a new data storage card.Typically, a data storage card such as the data storage card 200disclosed herein, is designed to hold 30-60 days of patient usageinformation.

The types of information that may be stored in the data card include,for example, the day, month, year and time of day (am or pm) as well asthe serial number of and the usage of the muscle stimulator. Such datais stored at the beginning of each data element. Other informationstored is whether treatment is present, the length of time in minutesthat the muscle stimulator was used, that is, that treatment wasprovided, the average intensity of the treatment used, the peakintensity of the treatment used, the number of times the treatment wasapplied within the relevant time period, the initial program mode data,any program changes made by the user and a reserve storage location. Inthat manner, the maximum number of bytes of data storage for one daycould preferably be 26 bytes. During treatment use by the patient, datais accumulated for the treatment period. When the muscle stimulator 100is turned off, the current treatment data is combined with the presenttreatment data and stored in an internal temporary storage area 1202.

When the muscle stimulator 100 is next turned on, the clock 1206 whichprovides the date and time is examined to determine if any 12 hourtreatment boundaries have been crossed. If they have, then thetemporarily stored data becomes the permanent data for the first 12 hourperiod beyond the last stored 12 hour period and that data is added tothe internal data storage 1202. Next, a determination is made of howmany more 12 hour periods have been crossed, and those are stored in theinternal data storage 1202 with zero data. Finally, the internallystored data is written to the storage device 1204 contained in the datastorage card 200. If no data storage card 200 is present, then no datais written to the card. The data written to the data storage card 200 iswritten as a block of data using the data stored in the internal storagearea 1202. The data is written beginning with the latest stored 12 hourperiod. That period is used to set the date and the other one time datadescribed above. Then, all available remaining data is written to thedata card. However, if there is more data in the internal data storagearea 1202 than can be stored on the data card 200, then only the latestdata which will fill up the storage element 1204 on the data storagecard 200 will be written to that storage element 1204. Thus, forexample, if a data storage card 200 has been removed from the musclestimulator 100 or similar type device, the next time a data storage card200 is inserted, the new data storage card will be filled immediatelywith all of the data stored in the internal data storage area 1202,including any "missing" data periods, as long as those "missing" periodsare within the data capacity of the data storage card 200.

Turning now to FIGS. 9 and 10, there is shown a side view and top viewof the data storage card guides 202, 204, which are constructed as thesame piece and mounted inside the muscle stimulator 100 in mirror imagefashion using a suitable bracket or other mounting mechanism. Each ofthe guides includes two mounting holes 900, 902 which may be used inconjunction with screws to attach the guides 200, 204 to suitablemounting brackets (not shown). Each of the guides 200, 204 include twoguide surfaces 1000, 1002, one of which is used by each of the guides asthe guide surface on which the elongated slots 600, 602 of the data card200 ride on. Each of the guides 200, 204 are preferably designed to bebidirectional, so it is immaterial which side they are used on. At theinward side of each of the guides 200, 204, an extended rounded portion1004, 1006 is formed, which is designed to mate with the detents 302,300 for aligning and securing the data storage card 200 within themuscle stimulator 100. FIGS. 7 and 8 show the guides 202, 204 mounted inthe muscle stimulator 100 and their relationship to the internal headerconnector 206. FIG. 11 shows an enlargement of the alignment andsecuring mechanism formed by the rounded portion 1004 of the guide 204and its cooperation with the detent 300 of the data card 200.

FIG. 12 is a schematic block diagram of the circuitry used by thepowered muscle stimulator 100 of the present invention. The musclestimulator 100 of the present invention, as previously discussed, ispowered by a rechargeable 6 volt nickel cadmium battery system 1208,which is recharged, as will be described later herein, by a batterycharger 1210, which may preferably be powered by standard 110 volthousehold electric current. As a safety feature, the muscle stimulator100 is designed to be inoperative while the battery system 1208 is beingcharged. A battery monitor circuit 1212 is connected between the batterysystem 1208 and the microcontroller 1200 so that the microcontroller canprovide an indication to the user by means of the LCD 114 under certainadverse battery conditions as will be described later herein. Themicrocontroller 1200, as will be described hereafter, serves to controland monitor all of the functions of the muscle stimulator 100.

As previously described, the powered muscle stimulator 100 of thepresent invention provides four isolated channels 1-4 capable ofindependently treating four separate muscle groups. Each of the fourchannels has an independent drive system 1218-1224, which includesindependent output power stages and transformers, in order to ensurechannel separation. A buzzer 1214 is provided such that audiblereinforcement of keystroke actions using the keypad 104-110 is providedto the user.

In operation, the patient first powers up the muscle stimulator 100using the on/off switch 102. If the patient does not desire to changethe settings entered into the internal memory 1202 of the musclestimulator 100, then the muscle stimulator 100 will be powered up in thepreviously set mode of operation. The default setting is the normalmode. In that normal mode, all four channels of the muscle stimulatoract synchronously, providing the stimulation pulse trains at the sametime, although the intensities of each channel are independentlycontrolled. This mode of operation allows the patient to independentlytreat up to four separate muscle groups simultaneously. If the patientdesires, an additional level of control for special situations has beenprovided, which is termed the alternate mode of operation. In thealternate mode of operation, channels 1 and 2 are operatedasynchronously with channels 3 and 4. Thus, when channels 1 and 2 arestimulating the muscles, channels 3 and 4 are off, and when channels 1and 2 are off, channels 3 and 4 are stimulating the muscles. The set onand off times are the same for all four channels in the normal mode.

During normal operation, the top line of the LCD display 114, which candisplay up to two lines of 16 characters per line, displays the currentsettings for the muscle stimulator 100. The bottom line displays theintensity levels selected by the user for each of the four channels. Inorder to provide visual acknowledgment of the operation of the musclestimulator, whenever outputs are being sent to a channel, the intensitylevel has an asterisk (*) displayed beside the intensity level toindicate that the output is being sent to that channel.

If the user wishes to increase the intensity on a certain channel, oneof the four rocker type of switches 104-110, which may preferably bedesigned as an elastomeric keypad, is pushed by the user. One end ofeach of the switches 104-110 serves to increase the intensity, while theother end of each of the switches serves to decrease the intensity onthat channel. When the user is finished a treatment session, the on/offswitch 102 is again depressed, turning off the muscle stimulator device100 at the end of the desired usage.

The four switches 104-110 are also used to change the settings of themuscle stimulator. In order to change the settings, the on/off switch102 is depressed for five seconds during the start-up sequence, whichautomatically places the muscle stimulator into the set-up mode. In theset-up mode, each of the rocker switches 104-110 can be used to changeone of the four operating parameters (contract time, relax time,treatment time and normal/alternating mode) of the muscle stimulator100. Once the patient has set the operating parameters of the musclestimulator as prescribed or desired, the patient then again depressesthe on/off switch 102 to store the new parameters. The values set by thepatient, based on the prescription and/or physician's instructions, areinternally stored in the internal storage 1202 for reuse during futuretreatments.

As previously described, an external data storage card 200 is used toprovide a usage monitoring capability, in conjunction with the internaldata storage 1202. The purpose of that monitoring capability is toprovide the physician and health care providers, as well as the providerof the muscle stimulator 100, with information documenting the usage ofthe muscle stimulator 100 by the patient. The cumulative usage of themuscle stimulator 100 by the patient in minutes as well as the averagestimulus setting in a 12 hour period (twice per day) is stored andrecorded for each channel, initially in the internal data storage 1202.While the internal memory 1202 is preferably capable of storing sixmonths of data, the usage information stored in the memory device 1204contained in the data storage card 200 is capable of storing only twomonths of data. The memory device 1204 which forms part of the datastorage card 200 is strictly a "write only" device, and allows only thereception and storage of data. No treatment data stored in either theinternal data storage 1202 or in the memory 1204 contained on the datastorage card 200 can be used for any control functions of the musclestimulator 100. The muscle stimulator 100 functions normally, whether ornot the data storage card 200 is mounted in the muscle stimulator 100.Once the patient is finished with treatment, the muscle stimulator 100is returned to its manufacturer or other provider and the internal datastored in the internal data storage area 1202 can then be retrieved.

The muscle stimulator 100 of the present invention generates analternating biphasic asymmetric balanced pulse pattern with a cyclefrequency of preferably 71 Hz. The primary pulse has a maximum width of415 microseconds, followed by the transformer coupled exponential decayback to zero base line. The biphasic pulses alternate direction,resulting in a pulse repetition rate of 142 pulses per second. Aspreviously described, the stimulus intensity is regulated by the patientby pressing the rocker switches 104-110. The voltage level is keptconstant. The resulting increase or decrease in stimulus intensity is aresult of the increasing or decreasing charge per pulse, which isapproximately equal to the pulse width times the pulse height.

The muscle stimulator 100 of the present invention uses a ramp on/offtype of stimulation, which increases the pulse width to the desiredsetting. The pulse generation system of the muscle stimulator 100preferably consists of an electronic switch such as a logic level FieldEffect Transistor, which is controlled by the microcontroller 1200. Whena pulse is to be generated, the microcontroller 1200 turns the FET"switch" on. That generates the start of the pulse. When themicrocontroller 1200 determines that the pulse is to end, it then turnsthe FET "switch" off. The FET "switch" applies power from the batterysystem 1208 directly across the output transformer primary windingswhich causes the pulse to be generated at the output side of thetransformer. Each of the drive circuits 1218-1224 includes such an FET"switch", as well as an output transformer, in a known manner. FIG. 14illustrates a drawing of a slowly increasing stimuli or ramp used toimplement this feature in the muscle stimulator 100 of the presentinvention.

As already described, the muscle stimulator 100 of the present inventiongenerates a series of pulse trains which generate output pulses for thetime period designated by the contract period selected by the user, andthen no pulses for the time period designated by the relax periodselected by the user. As shown in FIG. 14, at the beginning of eachpulse train, the pulse intensity is ramped up by the microcontroller1200 to allow a smooth transition from no pulses to the pulseintensities specified by the user. Similarly, at the end of the pulsetrain, the pulses are ramped back down to a zero intensity in order toachieve a smooth release of muscle contractions. The ramping feature iscontrolled by the microcontroller 1200 and is accomplished byincrementally increasing or decreasing the pulse widths until thedesired pulse width is achieved.

The load detect circuit 1226 shown in FIG. 12 may preferably consist ofan output voltage signal which is measured across a known loadresistance. That signal is amplified and feed back into theanalog-to-digital conversion system contained within the microcontroller1200, which allows a precise measurement of the actual load experiencedacross the output of the transformer contained in each of the four drivecircuits 1218-1224. That measurement allows the microcontroller 1200 todetect both open circuits (that is, no load conditions) and shortcircuit conditions, which allows the microcontroller 1200 to shut downthe control signals going to the pulse generation circuits which formpart of the drive circuits 1218-1224. Thus, under open or short circuitconditions, the load detection circuit 1226 operates to shut down thegeneration of pulses by the muscle stimulator 100.

A watchdog system 1216 is also provided with which to monitor themicrocontroller 1200 to ensure that the microcontroller 1200 isoperating and issuing instructions. The watchdog system 1216 operatesusing a "counter". If the "counter" reaches a certain predeterminedvalue, then it operates to shut down the microcontroller 1200 and thusthe muscle stimulator 100. During normal operation, the microcontroller1200 prevents such a shut down from occurring by always resetting the"counter" of the watchdog system 1216 back to zero well before themaximum counter value is reached. In that manner, if the microcontroller1200 becomes non-operational for any reason, the counter of the watchdogsystem 1216 would reach the maximum predetermined value and thus shutdown the muscle stimulator 100.

FIG. 13 illustrates, in schematic block diagram form, the firmwarepermanently stored in the read only memory of the microcontroller 1200which is used to operate and control the muscle stimulator 100 of thepresent invention. The firmware is controlled by a Foreground ExecutiveModule, which provides executive control of the muscle stimulator 100from start-up to shut-down. This module is programmed as a "statemachine" such that the firmware controls the operational state of themicrocontroller 1200 based on inputs received from the circuitry of themuscle stimulator 100.

As previously described, the primary module which operates the outputchannel circuits is the pulse generator module, which forms part of thedrive circuits 1218-1224. That module is started by the ForegroundExecutive Module at the startup state 1300, when the on key 102 isdepressed. The background pulse generator module is operated in anindependent interrupt driven fashion and functions using data suppliedby the Foreground Executive Module, which data has been inputted duringthe parameter modify or programming stage 1302. As previously described,if the on key 102 is released in less than 5 seconds after it isdepressed, the muscle stimulator 100 enters the running state 1304,during which the treatment of the patient is provided.

The microcontroller 1200 constantly monitors the operation of thecircuitry of the muscle stimulator 100 of the present invention. Forexample, the firmware monitors the operational frequencies of thebackground pulse generators which form part of the drives 1218-1224against an independent frequency to ensure that each of thoseoperational frequencies do not become corrupted. Such monitoring occursin the running state 1304 and is accomplished through the use of theclock monitoring subsystem of the microcontroller 1200. The clockmonitor subsystem of the microcontroller 1200 monitors the frequency ofthe clock oscillator integrated circuit which determines the actual"speed" or frequency of the operation of the microcontroller 1200 andall the timing actions which it controls. In the event that any of thefrequencies become corrupted, the operational state of the firmwareshifts to the suspend and error handling state 1310, which displays anerror message for the user and then causes the firmware to enter theending state 1306 which sets up the muscle stimulator for shut-down. Theerrors are handled in the suspend and error handling state 1310, theyare then displayed as a warning on the LCD display 114 in the errorwarning state 1312 and the muscle stimulator 100 then enters the stopstage 1314, which serves to turn off the muscle stimulator circuitry.

In addition, the firmware also monitors the load on each channel, usingthe load detect circuit 1226. Again, that monitoring occurs during therunning state 1304. In the event that no load is detected, indicatingeither an open or shorted condition, the firmware again passes to thesuspended error handling state 1310, and then passes through the endingstate 1306, the error warning state 1312 and enters the stopped state1314, as previously described. In a similar fashion, the battery system1208 is monitored by the battery monitor 1212 during the running state1304 and, in the event it is determined that there will shortly beinsufficient power to properly operate the microcontroller 1200, themuscle stimulator 100 is shut down, in a manner similar to thatdescribed above in connection with a corrupted background pulsegenerator frequency or a no load detection condition.

The firmware also accumulates and stores treatment data for eachchannel, both in the internal memory 1202 and in the memory 1204 of theexternal data storage card 200. When the patient completes the treatmentsession, the firmware writes that data to the internal storage 1202prior to the shut down of the microcontroller 1200. The treatment datais stored on the data storage card 200 by 12 hour time increments. Foreach 12 hour period, the cumulative patient usage of the musclestimulator in minutes is recorded, as well as the average stimulussetting. The patient usage data is transferred from the internal datastorage 1202 to the storage device 1204 contained on the data storagecard during the start-up sequence of the muscle stimulator 100.

The settings for the contract or on time, the relax or off time, thetreatment mode (whether normal or alternate) and the length of thetreatment are also stored for the user in the microcontroller 1200memory within the muscle stimulator 100. Those four items are alsodisplayed for the user on the LCD screen 114. Those program modeparameters can be reset at any time by entering the program set-up modeduring a start-up sequence of the muscle stimulator 100, in the mannerpreviously discussed. Once the program set-up mode has been entered, theLCD screen 114 displays the program change screen which allows the user,by manipulating the rocker switches 104-110, to change the correspondingprogram mode parameter displayed on the screen. For example, using thechannel 1 switch 104 changes the contract time, using the channel 2switch 106 changes the relax time, using the channel 3 switch 108toggles between the normal and alternate modes and using the channel 4switch 110 increases or decreases the treatment time.

The battery system 1208 is charged during a quick recharge cycle by thebattery charger 1210. During the charging cycle, the muscle stimulatoris in the charging state 1318, and cannot operate. The battery monitor1212 as well as the microcontroller 1200 determine the amount of chargeneeded by the battery system 1208. If the battery system 1208 issufficiently low, then the battery system will be charged until thebattery voltage begins to show a decline, then the charging circuitreverts to a "trickle" charge mode in order to allow maintenance of afully charged battery at all times.

Additional safety features of the muscle stimulator 100 of the presentinvention include a large diameter pin 128 at the end of each of the padcables 126, such that the pad cable 126 cannot be accidentally pluggedinto a 110 volt household electrical outlet and cause electrical shockand damage to the pads and cable, a battery charger cable with a pinthat plugs only into the battery charger jack 124 thus preventing thebattery charger cable from being accidentally plugged into a channeljack, which could damage the muscle stimulator 100 and a plug connectiondetector (load detect circuit 1226) which is designed to detect if aconnection between the pads, cables 126 and the muscle stimulator 100 isfaulty. If, after start-up, a faulty connection is detected, the musclestimulator 100 will not start. If, during operation, a connectionbecomes loose, the circuitry of the muscle stimulator 100 will beautomatically shut-off. The plug connection monitor thus assures theuser that all channel connections are good.

The firmware used with the muscle stimulator 100 of the presentinvention also includes, as a safety feature, a start treatment channelsetting. That feature is designed to prevent, at the start of atreatment, a channel output to be set above zero. That assures that theuser will not receive an abrupt muscle contraction when starting atreatment. Thus, when starting a treatment, the muscle stimulator 100begins operation with all channel intensity settings at zero. If a padis removed from the skin during treatment, the muscle stimulator 100automatically resets the channel to zero. If a pad cable is unpluggedfrom the muscle stimulator 100 during treatment, the intensity of thatchannel is reset to zero.

In addition to the start treatment channel setting safety feature, themuscle stimulator 100 of the present invention also includes a channelincrease/decrease limit feature, which is designed so that the channeloutput level can only be changed one digit at a time. Thus, pressing therespective channel rocker switch 104-110 will change the outputcontrolled by that switch by only one digit. That assures that the userwill not receive a rapid increase or decrease in muscle contractionduring treatment if the rocker switch were continually depressed.

The muscle stimulator 100 of the present invention also includes infirmware a monitor which is designed to constantly monitor the frequencyand width of the waveform being applied to each of the pad cables, whichis the pattern of output which creates a muscle contraction. If thewaveform changes from the pattern it is designed to generate, the musclestimulator is automatically shut-off. That assures that the user willreceive the effective and comfortable contraction designed to beprovided by the muscle stimulator 100. As a final safety feature, themuscle stimulator 100 of the present invention is designed to constantlymonitor the liquid crystal display 114. If it is determined that thedisplay is not operating properly, then the muscle stimulator 100 isautomatically shut-off. In that manner, the patient receives a constantand accurate display of information concerning the operation of themuscle stimulator 100. When the muscle stimulator 100 is first turned onusing the switch 102, the LCD 114 displays the default settings for eachof the contract time, relax time, mode and treatment time. If those arethe prescription settings for the particular patient using that musclestimulator 100, then there is no need to change the settings. Otherwise,the settings are changed as described previously.

As will be obvious to those of ordinary skill in the art, the data card200 and its electrical and mechanical structure are such that it canreadily be adopted for use in many types of devices, including, forexample, any Class II type of device which is designed for unsupervisedpatient use. Likewise, such a data card could be used in various othertypes of devices, whether for a supervised patient use or otherwise.

Although only a preferred embodiment is specifically illustrated anddescribed herein, it will be appreciated that many modifications andvariations of the present invention are possible in light of the aboveteachings and within the purview of the appended claims withoutdeparting from the spirit and intended scope of the invention.

We claim:
 1. A portable muscle stimulator for generating a plurality ofmuscle stimulating signals for application to a patient using aplurality of electrodes, comprising:a plurality of independently drivenchannels connected respectively to a like plurality of electrodes forindependently treating a like plurality of separate muscle groups of apatient, each of said plurality of independently driven channelsincluding its own drive circuit; a digital data processor connected toeach of said drive circuits for each providing a drive control signalfor causing each of said drive circuits to generate said plurality ofmuscle stimulating signals; each of said drive control signals causingits respective drive circuit to generate a muscle stimulating signal asa series of on and off pulses over a given time period; and said pulseshaving a predetermined constant voltage and an intensity and a waveformshape such that the beginning of said pulse has a ramp portion from zeroto maximum intensity, a middle portion constant at maximum intensity,and an end ramp portion from maximum intensity to zero, such that thereis a smooth transition from no pulses to the maximum pulse intensity andthen back to no pulses in order to provide smooth muscle contractionsand release of contractions.
 2. The portable muscle stimulator of claim1, wherein said maximum pulse intensity is selectable by said patient.3. The portable muscle stimulator of claim 2, wherein said patientselects pulse intensity by increasing or decreasing charge per pulse. 4.The portable muscle stimulator of claim 1, wherein each of said pulseshas a constant voltage level at said maximum intensity portion of saidpulses.
 5. The portable muscle stimulator of claim 1, wherein the timeperiods during which pulses are generated and not generated areselectable by said patient.
 6. The portable muscle stimulator of claim1, wherein pulse intensity for each of said plurality of independentlydriven channels is separately selectable by said patient.
 7. Theportable muscle stimulator of claim 1, wherein each of said plurality ofindependently driven channels further includes a load detect circuitconnected between each respective electrode and each respective drivecircuit, for providing a feedback signal to said digital data processorindicative of an actual load experienced by each respective one of saidplurality of drive circuits.
 8. The portable muscle stimulator of claim7, wherein said digital data processor receives said feedback signalsfrom each load detect circuit and detects whether short or open circuitconditions exist in each of said plurality of independently drivenchannels.
 9. The portable muscle stimulator of claim 8, wherein saiddigital data processor stops the generation of muscle stimulatingsignals in any of said independently driven channels in which at leastone of an open and short circuit condition is detected.
 10. The portablemuscle stimulator of claim 1, wherein both of said ramp portions of saidwaveform shape are symmetrical with each other.
 11. The portable musclestimulator of claim 1, wherein each of said plurality of independentlydriven channels is synchronously driven.
 12. The portable musclestimulator of claim 1, wherein the maximum intensity of said pulses ineach of said independently driven channels is independently controllableby said patient.
 13. The portable muscle stimulator of claim 1, whereineach pair of said plurality of independently driven channels issynchronously driven within each pair and asynchronously driven withrespect to each other pair of driven channels.
 14. The portable musclestimulator of claim 1, wherein an average value of the intensity of eachof said pulses in each independently driven channel is calculated andstored for later review.
 15. The portable muscle stimulator of claim 14,wherein said average values are stored in removable data storage whichcan be removed from said portable muscle stimulator without disablingsaid stimulator and sent to a remote location for review for compliancewith a predetermined treatment plan for said patient.
 16. A portablemuscle stimulator for generating a plurality of muscle stimulatingsignals for application to a patient using a plurality of electrodes,comprising:a microcontroller; a plurality of switches, each connected tobe operated by said microcontroller; a like plurality of outputtransformers, connected such that power stored in said portable musclestimulator can be applied to said output transformers by said pluralityof switches; said microcontroller generating a series of pulse trainsfor generating output pulses by said plurality of output transformersfor a first time period predetermined by a contract period selected bysaid patient and then no pulses for a second time period predeterminedby a relaxation period selected by said patient, said output pulseshaving a predetermined constant voltage; and wherein saidmicrocontroller ramps up the intensity of each pulse at the beginning ofeach pulse train to an intensity preselected by said patient and thenramps down said intensity to zero at the end of said pulse train inorder to allow a smooth transition from zero to maximum intensity tozero intensity, thereby achieving a smooth contraction and release ofsaid patient's muscles.
 17. The portable muscle stimulator of claim 16,wherein said ramping is controlled by said microcontroller and isaccomplished by incrementally increasing or decreasing pulse widthsuntil a desired pulse width is achieved.
 18. The portable musclestimulator of claim 16, wherein each of said pulses has a constantvoltage level at said maximum intensity portion of said pulses.
 19. Theportable muscle stimulator of claim 16, wherein said patient selectspulse intensity by increasing or decreasing charge per pulse.
 20. Theportable muscle stimulator of claim 16, wherein both said ramp up andsaid ramp down of said intensity produce symmetrical ramp waveforms. 21.A portable muscle stimulator for generating a plurality of musclestimulating signals for application to a patient using a plurality ofelectrodes, comprising:at least three independently driven channelsconnected respectively to a like plurality of electrodes forindependently treating a like plurality of separate muscle groups of apatient, each of said plurality of independently driven channelsincluding its own drive circuit; a digital data processor connected toeach of said drive circuits for each providing a drive control signalfor causing each of said drive circuits to generate said plurality ofmuscle stimulating signals; each of said drive control signals causingits respective drive circuit to generate a muscle stimulating signal asa series of on and off pulses over a given time period; and said pulseshaving an intensity and a waveform shape such that the beginning of saidpulse has a ramp portion from zero to maximum intensity, a middleportion constant at maximum intensity, and an end ramp portion frommaximum intensity to zero, such that there is a smooth transition fromno pulses to the maximum pulse intensity and then back to no pulses inorder to provide smooth muscle contractions and release of contractions.22. The portable muscle stimulator of claim 21, wherein said maximumpulse intensity is selectable by said patient.
 23. The portable musclestimulator of claim 22, wherein said patient selects pulse intensity byincreasing or decreasing charge per pulse.
 24. The portable musclestimulator of claim 21, wherein each of said pulses has a constantvoltage level at said maximum intensity portion of said pulses.
 25. Theportable muscle stimulator of claim 21, wherein the time periods duringwhich pulses are generated and not generated are selectable by saidpatient.
 26. The portable muscle stimulator of claim 21, wherein pulseintensity for each of said at least three independently driven channelsis separately selectable by said patient.
 27. The portable musclestimulator of claim 21, wherein each of said at least threeindependently driven channels further includes a load detect circuitconnected between each respective electrode and each respective drivecircuit, for providing a feedback signal to said digital data processorindicative of an actual load experienced by each respective one of saidplurality of drive circuits.
 28. The portable muscle stimulator of claim27, wherein said digital data processor receives said feedback signalsfrom each load detect circuit and detects whether short or open circuitconditions exist in each of said at least three independently drivenchannels.
 29. The portable muscle stimulator of claim 28, wherein saiddigital data processor stops the generation of muscle stimulatingsignals in any of said independently driven channels in which at leastone of an open and short circuit condition is detected.
 30. The portablemuscle stimulator of claim 21, wherein both of said ramp portions ofsaid waveform shape are symmetrical with each other.
 31. The portablemuscle stimulator of claim 21, wherein each of said at least threeindependently driven channels is synchronously driven.
 32. The portablemuscle stimulator of claim 21, wherein the maximum intensity of saidpulses in each of said independently driven channels is independentlycontrollable by said patient.
 33. The portable muscle stimulator ofclaim 21, having four independently driven channels operated in pairs,wherein each of said independently driven channels is synchronouslydriven within each pair and asynchronously driven with respect to theother pair of driven channels.
 34. The portable muscle stimulator ofclaim 21, wherein an average value of the intensity of each of saidpulses in each independently driven channel is calculated and stored forlater review.
 35. The portable muscle stimulator of claim 34, whereinsaid average values are stored in removable data storage which can beremoved from said portable muscle stimulator without disabling saidstimulator and sent to a remote location for review for compliance witha predetermined treatment plan for said patient.
 36. The portable musclestimulator of claim 21, wherein said pulses have apredetermined constantvoltage.
 37. A portable muscle stimulator for generating a plurality ofmuscle stimulating signals for application to a patient using aplurality of electrodes, comprising:a plurality of independently drivenchannels connected respectively to a like plurality of electrodes forindependently treating a like plurality of separate muscle groups of apatient, each of said plurality of independently driven channelsincluding its own drive circuit; a digital data processor connected toeach of said drive circuits for each providing a drive control signalfor causing each of said drive circuits to generate said plurality ofmuscle stimulating signals; each of said drive control signals causingits respective drive circuit to generate a muscle stimulating signal asa series of on and off pulses over a given time period; and said pulseshaving an intensity controlled by increasing or decreasing charge perpulse and a waveform shape such that the beginning of said pulse has aramp portion from zero to maximum intensity, a middle portion constantat maximum intensity, and an end ramp portion from maximum intensity tozero, such that there is a smooth transition from no pulses to themaximum pulse intensity and then back to no pulses in order to providesmooth muscle contractions and release of contractions.
 38. A portablemuscle stimulator for generating a plurality of muscle stimulatingsignals for application to a patient using a plurality of electrodes,comprising:a plurality of independently driven channels connectedrespectively to a like plurality of electrodes for independentlytreating a like plurality of separate muscle groups of a patient, eachof said plurality of independently driven channels including its owndrive circuit; a digital data processor connected to each of said drivecircuits for each providing a drive control signal for causing each ofsaid drive circuits to generate said plurality of muscle stimulatingsignals; each of said plurality of independently driven channels furtherincluding a load detect circuit connected between each respectiveelectrode and each respective drive circuit, for providing a feedbacksignal to said digital data processor indicative of an actual loadexperienced by each respective one of said plurality of drive circuits;each of said drive control signals causing its respective drive circuitto generate a muscle stimulating signal as a series of on and off pulsesover a given time period; and said pulses having an intensity and awaveform shape such that the beginning of said pulse has a ramp portionfrom zero to maximum intensity, a middle portion constant at maximumintensity, and an end ramp portion from maximum intensity to zero, suchthat there is a smooth transition from no pulses to the maximum pulseintensity and then back to no pulses in order to provide smooth musclecontractions and release of contractions.
 39. The portable musclestimulator of claim 38, wherein said digital data processor receivessaid feedback signals from each load detect circuit and detects whethershort or open circuit conditions exist in each of said plurality ofindependently driven channels.
 40. The portable muscle stimulator ofclaim 39, wherein said digital data processor stops the generation ofmuscle stimulating signals in any of said independently driven channelsin which at least one of an open and short circuit condition isdetected.
 41. A portable muscle stimulator for generating a plurality ofmuscle stimulating signals for application to a patient using aplurality of electrodes, comprising:a plurality of independently drivenchannels connected respectively to a like plurality of electrodes forindependently treating a like plurality of separate muscle groups of apatient, each of said plurality of independently driven channelsincluding its own drive circuit; a digital data processor connected toeach of said drive circuits for each providing a drive control signalfor causing each of said drive circuits to generate said plurality ofmuscle stimulating signals; said digital data processor calculating andstoring for later review an average value of the intensity of each ofsaid pulses in each independently driven channel; each of said drivecontrol signals causing its respective drive circuit to generate amuscle stimulating signal as a series of on and off pulses over a giventime period; and said pulses having an intensity and a waveform shapesuch that the beginning of said pulse has a ramp portion from zero tomaximum intensity, a middle portion constant at maximum intensity, andan end ramp portion from maximum intensity to zero, such that there is asmooth transition from no pulses to the maximum pulse intensity and thenback to no pulses in order to provide smooth muscle contractions andrelease of contractions.
 42. The portable muscle stimulator of claim 41,wherein said average values are stored in removable data storage whichcan be removed from said portable muscle stimulator without disablingsaid stimulator and sent to a remote location for review for compliancewith a predetermined treatment plan for said patient.